Microwave detectors based on granular high-Tc thin films

The detecting and mixing properties of microstrip superconducting Y-Ba-Cu-O and Bi-Ca-Sr-Cu-O thin-film structures deposited on various substrates have been investigated. The device performance was tested in the 22-, 55-, and 110-GHz frequency bands at temperatures ranging from 100 K to about 50 K. The sensitivity obtained at 110 GHz was comparable to that of crystalline detectors. Mixing experiments were performed in the 25-GHz frequency band and indicated that the detector response time is less than 40 ps. The intermediate frequency was varied from 50 MHz to 5 GHz without any decrease in the mixer output up to 3 GHz. Auxiliary emission measurements performed at 12 GHz and down to 4.2 K revealed that the detector low-temperature performance limit is associated with microwave radiation from clusters of intergrain weak links arranged in multiloop quantum interferometers